1. Technical Field
The present invention generally relates to the production of direct expanded (i.e., puff extruded) farinaceous food products utilizing a novel extruder die apparatus. More specifically, the present invention is concerned with an improved extruder die assembly and method for using same to add a fluid additive into an extrudable food mass while improving the dimensional quality of the resulting direct expanded food products. In particular, the improved extruder die assembly of the present invention may impart a distinct colored and/or flavored pattern into the extrudable food mass during extrusion while also improving the dimensional quality of the resulting complexly shaped direct expanded food products. The present invention also includes a method and composition for producing a dried, flavored, direct-expanded food product requiring no post-extrusion drying or seasoning process by utilizing the improved extruder die assembly.
2. Description of the Related Art
The use of extrusion devices is prevalent in a number of industries, especially the food industry. The use of extrusion devices in the preparation of direct expanded food products is long practiced. Utilized to produce a variety of products such as ready-to-eat (R-T-E) cereals, snack foods and confections, extrusion remains prominent among food processes because of its versatility and efficiency.
Food processes utilizing extrusion devices typically include an edible substance such as dough which is introduced into a device and conveyed via a screw pump to an inlet where the substance is forced through an extruder die assembly. The extruder die assembly may perform a variety of functions: it may form or shape the extrudate; it may divide the extrudate into a multiple extrudates; it may inject an additive substance into the extrudate; and it may compress and reduce the cross-sectional area of the extrudate. Examples of devices used for extrusion of food products are illustrated in U.S. Pat. Nos. 2,858,217; 3,314,381; and 5,639,485. While extrusion dies have evolved over the years, the method by which an additive substance is supplied and injected into the extrudate has remained essentially unchanged.
For Example, in U.S. Pat. No. 2,858,217 to Benson, the introduction of coloring matter, such as a colored liquid dye, is accomplished via a series of apertures 40, 42, 44 disposed in the bridging strips 32, 34, 36 and supplied by horizontal passages 52, 54, 55 which are in fluid communication with the dye reservoir 46. The supplying of the liquid dye from the dye reservoir 46 to series of apertures 40, 42, 46 is by means of gravitational force. According to the Benson '217 device, dough material 18 is extruded through a divider block 22 which forces the dough material 18 to divide or spread around the bridging strips 32, 34, 36 so that voids 38 are formed into which the coloring matter is introduced via the series of apertures 40, 42, 44.
Similarly, in U.S. Pat. No. 3,314,381 to Fries et al., the fluid injection assembly is comprised of a hollow tubular injection member 29 in a helical spiral configuration, which includes a bore 37 through which pressurized injection fluid is supplied from a source 25 to a plurality of longitudinally spaced bores 39 into a distributing channel 38. The fluid along the length of channel 38 is injected into the passing dough as a substantially longitudinally continuous spiral band extending from substantially the central axis of the dough to either the outer face of the dough or a point short thereof. However, the Fries et al. '381 device is primarily adapted to relatively low pressure comestible extrusions.
Finally, U.S. Pat. No. 5,639,485 to Weinstein et al. and its related patents, disclose a method and apparatus for adding additives in flowing dough to make complexly patterned multicolored extrudates. The Weinstein et al. '485 invention and its progeny all disclose a high pressure extrusion device comprising an extruder die insert 20 which includes means for imparting at least one interstitial gap in the flowing dough by means of a plurality of dividing passageways (e.g., 44, 45, 46) formed by die dividing members 47. An additive (e.g., a food color or a second colored dough) may be injected via a plurality or array of evenly spaced food color injection ports 48 formed on the downstream side of die dividing member 47. The injection ports 48 are in fluid communication with a pressurized color supply 18 by means of a supply ports 52, 54, 56 and supply passageway 50. The color fluid tends to fill the interstitial gaps in the flowing dough between passageways (e.g., 44, 45, 46) formed by and behind the die dividing members 47 to create a line in the shape of dividing members 47 in the extruded dough. The die insert 20 also includes notches 57 which are used to isolate the color fluid injected into the interstitial gap from spreading to the interior surface wall of die insert 20 thereby reducing if not eliminating the leakage on color fluid onto the outside of the extruded dough. Additionally, the die insert 20 can further include a means for sealing (e.g., “O” rings 60 and 62 as depicted) the color fluid supply reservoir 58 against premature admixture with dough.
In addition to the die insert element, the Weinstein et al. '485 invention also comprises a reducing passageway 25 whereby the extrudate's cross-sectional area is significantly reduced. At high operating pressures, the convergence of the passageway 25 inherently creates a significant back pressure on the downstream side of the extruder die insert 20 which, in turn, can contribute to and promote the clogging of the individual injection ports 48. Moreover, the utilization of notches 57, sealing means 60, 62 and multiple enclosed injection ports 48 further complicates the design of the die insert making it harder to clean and maintain. Finally, injecting color fluid at discrete locations into downstream voids or interstitial gaps to disperse the fluid in a generally uniform manner requires precise control of flow rates, internal pressures, and viscosity of the extrudate and various additives. Furthermore, the design of each die insert 20 is limited to the physical constraints imposed by the previously mentioned design elements.
What is needed is an extruder die assembly capable of operating at a variety of operating pressures which has improved seal characteristics and is simpler and easier to maintain and whose injection mechanism is less prone to clogging and blockages.
In addition, extrusion devices are increasingly utilized to impart heat to the base substance during its transit through the extruder device. Typically, a casing surrounding the extrusion chamber is adapted to impart heat to the substance in accordance with practices commonly known in the art. For example, cooker extruders are used to prepare cooked dough extrudates that may then be formed into individual cereal or snack pieces, and subsequently baked or fried.
One variation of cooker extruders that is increasingly popular comprises an extruder wherein the conditions of the extruder and the cooked cereal dough are such that the dough puffs immediately upon being extruded and is cut into individual puffed pieces at the die head. Such a process is referred to generally as “direct expansion” or “puff extrusion.”
The flavoring of such extruded food products typically comprises either flavoring the base substance prior to its introduction to the extruder device (i.e., adding a flavoring to the base substance within the extruder device wherein it is admixed utilizing a screw pump mechanism) or flavoring the resulting extruded food piece subsequent to the extrusion process. However, inducing heat to the base substance during an extrusion process adversely affects the flavoring of the resulting extruded food product. Many flavoring are particularly sensitive to heat induced during the manufacturing process. For example, spicy flavorings (e.g., green pepper, chipotle, and jalapeño) and salty dairy flavors (e.g., cheddar cheese and sour cream) are particularly susceptible to flavor diminishment or deterioration when exposed to heat for an extended period of time during a direct expansion extrusion process. Even sweet flavorings (e.g., strawberry, chocolate, vanilla, etc.), while more heat tolerant than other flavoring, are, nevertheless, somewhat degraded when exposed to heat during the manufacturing process. Thus, the flavoring of direct expansion food products usually occurs during a separate seasoning step, which occurs subsequent to the direct expansion extrusion process. Flavorings are typically sprinkled on and admixed with a mass of direct expansion food product on a conveyor belt mechanism or in a tumbling drum mechanism. The tumbling mechanism ensures even coverage of the extruded product.
While the adverse effects caused by heat on flavorings can be avoided by utilizing an extruder mechanism which does not induce heat to the base substance during an extrusion process, the resulting flavored extruded pieces will typically still require a subsequent drying process. Moreover, the dried, flavored, extruded pieces will also have to be subsequently baked or fried, which will similarly affect adversely the quality of the flavoring.
Thus, a need also exists for a more efficient system for flavoring extruded food products during a production run of a cooker extrusion device. In this regard, it would be particularly desirable if the seasoning or flavoring of direct expanded food products could be accomplished in a one-step extrusion process (i.e., without a separate seasoning step subsequent to the extrusion process and without a substantial degradation of heat sensitive flavorings injected prior to the extrusion process).
Another problematic aspect of direct expansion or puff extrusion devices involves the dimensional quality of the resulting direct expanded food products. Upon exiting the extruder die assembly of a puff extrusion device, the extruded mass is directly expanded (e.g., via flash puffing) and typically cut into individual pieces using a reciprocating blade mechanism. The resulting individual pieces typically have a uniform, puffed shape with a cross-sectional shape generally corresponding to the outline of the forming die's exit port. While the characteristics of the resulting individual pieces are satisfactory for simple geometric shapes (e.g., spheres, ovoids, and crescents), the design details of more complex shapes tend to be obscured or eliminated.
For example, FIG. 1a shows the exit face 12 of a forming die 10 used in prior art extruder die assembly. Included within the periphery of the exit face 12 is a complexly shaped exit port 14. The outline 16 of exit port 14 is designed to resemble a hand with four distinct appendages or fingers. When the forming die 10 is utilized in conjunction with a conventional direct expanded food process, the resulting product is a uniformly puffed food piece 18 as shown in FIG. 1b. While the shape of the outline 16 of exit port 14 is somewhat discernable in food piece 18, the design details of the four distinct appendages is generally diminished and obscured. The individual dimensional aspects of the four distinct appendages are simply absorbed by the dimensional aspects of the palm area of the outline 16 of exit port 14.
A need, therefore, exists for an improved apparatus and method for imparting a distinct colored and/or flavored pattern into an extrudable food mass during the extrusion process while enhancing the quality of dimensional design aspects of extruded, complexly shaped, direct expanded food products.